1. Field of the Invention
The present invention relates in general to an apparatus and a method for producing variable configuration dies which are used for producing casted metal dies and/or molded plastic dies of small lots, and more particularly, to an apparatus and a method for producing the variable configuration dies by using a plurality of metal pins.
2. Description of the Prior Art
Sheet metal parts with compound curvative shapes are typically produced by deforming the sheet metal between A pair of metal dies. Owing to variations in sheet metal material properties, however, such dies require substantial development time.
In order to reduce or eliminate such die development time, there have been hitherto proposed several measures which create a sheet metal forming process that is capable of producing small lots without prohibitive tooling costs. Some of them are described in Japanese Patent First Provisional Publications Nos. 56-36343 and 61-47217.
In the measure disclosed by these publications, a plurality of metal pins are used for producing a variable configuration die. That is, the pins are parallelly arranged and piled in a manner to form a discrete recessed die surface with their one ends. For forming the recessed die surface, some of the piled pins are axially displaced with respect to the remaining piled pins. After the piled pins are tightly bound to produce a fixed variable configuration die, the same is so arranged that the recessed die surface faces upward. Then, a melted metal is casted into the recess of the die. After the metal is cooled, the same is removed from the die. With this, a casted metal die having a convex die surface is produced.
In the process of producing the variable configuration die, the displacement of the pins is achieved by an ultrasonic vibration shifting means or the like.
However, this pin shifting method has the following drawback.
That is, during the axial movement of the selected pins by the shifting means, it tends to occur that neighboring pins of the selected pins are inevitably drawn by the same due to frictional forces produced therebetween. This phenomenon causes lowering in configuration accuracy of the shaped discrete die surface.
In order to eliminate this drawback, Japanese Patent First Provisional Publication 61-276741 proposes a measure in which certain clearances are provided between neighboring pins. Due to provision of such clearances, the undesired pin drawing phenomenon does not occur. However, also in this case, the discrete die surface produced becomes rough due to provision of marked blanks on the die surface.